1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier or laser beam printer equipped with an original scanning apparatus typified by an automatic document feeder unit (ADF) or with an ADF.
2. Description of the Related Art
Conventionally, in an image forming apparatus of this type, an original conveyance path leading to an original conveyance type of an original scanning unit and a recording material conveyance path of an image forming unit for a recording material are configured independently of each other. That is, with respect to each of the original and the recording material, a sheet feeding unit, a guide member making up a predetermined conveyance route, plural conveyance rollers, a motor configured to drive the conveyance rollers, and a sheet discharge unit are disposed independently of one another. This inevitably complicates an overall mechanism of the image forming apparatus and increases the cost and apparatus size. Thus, for example, Japanese Patent Application Laid-Open No. 2006-232467 proposes to simplify a conveyance mechanism and achieve cost and size reductions by combining an original conveyance path and a recording material conveyance path into a common path by disposing an original scanning unit in a double-side conveyance route of a recording material.
Furthermore, when the original conveyance path and recording material conveyance path are combined into a common path, an original can be used as recording material after an image is read, enabling overwrite printing on the original. Using this overwrite printing function, for example, Japanese Patent Application Laid-Open No. 2006-126488 and No. 2010-197550 disclose techniques for filling a printed image on an original for the purpose of information protection. Japanese Patent Application Laid-Open No. 2006-126488 discloses a technique for performing a filling process by selecting an image pattern or solid image as an overwriting image based on information about a mark printed on a read original; and doing overwrite printing regularly on an entire surface of the original using the selected overwriting image. Also, Japanese Patent Application Laid-Open No. 2010-197550 discloses a technique for performing a filling process by detecting edges of inscribed information in an arbitrary fill area on a read original; and filling an outer area bordered by the edges with a solid image.
However, with the technique disclosed in Japanese Patent Application Laid-Open No. 2006-126488 since overwrite printing is done on the entire surface of the original using an image pattern or solid image, even that part of the original which does not need information protection is subjected to overwrite printing. Furthermore, since the overwrite printing is done with a regular image pattern, the inscribed information is legible in some cases, failing to ensure sufficient security.
Also, with the technique disclosed in Japanese Patent Application Laid-Open No. 2010-197550 since an arbitrary area on the original is filled with a solid image except for the inscribed information, toner is consumed more than necessary, which is not desirable for the user from the viewpoint of source and cost savings.